1. Field of the Invention
The invention relates to television systems, more particularly for progressively scanned, digital televisions.
2. Background of the Invention
Broadcast television signals typically arrive at the receiver in interlaced format. That is, each video frame to be displayed arrives as two fields. The first field contains either the even-numbered lines or the odd-numbered lines. The second field contains the opposite set of lines.
The television displays the frames such that the viewer cannot really tell that they are two fields. However, recent innovations in the broadcast television area have started to do progressive scanning. In progressive scanning (proscan), the interlaced fields are combined before display, and the entire frame is displayed. In a cathode-ray tube (CRT) television, this means that the electron gun or guns that scan the picture do so with the entire frame of data rather than scanning either the even or odd lines first, then following with the opposite lines.
In some embodiments of television systems, no CRT is used. These televisions use arrays of individually controllable elements, such as liquid crystal devices, or digital micromirror devices. etc. (LCDs or DMDs, respectively). Because there is no scanning gun in these systems, they will typically have to de-interlace the fields before display, then put the entire frame onto the activation circuitry for the array of individual elements.
This can cause problems by raising the system cost and requiring higher level circuitry to perform these functions. Without the ability to implement proscan, however, the other advantages of using spatial light modulators, including completely digital television (digital from input to output) and sharper pictures with better resolution, become overshadowed by the high cost.
A method is needed, therefore, to allow system using spatial light modulators to convert from interlaced to proscan without a sharp increase in the system cost.